SAT Question 8917ce38: Ratios Rates Proportional Relationships And Units answer and explanation with Desmos solution

Choice A is correct. Since $1$ kilometer is equal to $1,000$ meters, it follows that $90$ kilometers is equal to $90\times 1,000=90,000$ meters. Since $1$ hour is equal to $60$ minutes and $1$ minute is equal to $60$ seconds, it follows that $1$ hour is equal to $60\times 60=3,600$ seconds. Now $\frac{90\text{ kilometers}}{1\text{ hour}}$ is equal to $\frac{90,000\text{ meters}}{3,600\text{ seconds}}$, which reduces to $\frac{25\text{ meters}}{1\text{ second}}$ or $25$ meters per second.